Merck Manual

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Common GI Parasites of Small Ruminants

Common GI Parasites of Small Ruminants

Name

Size

Anatomical Location of Adults

Appearance on Fecal Flotation

Extent of Pathogenicity

Haemonchus spp (barber's pole worm, large stomach worm, wire worm)

Adults: 10–30 mm

Eggs: 65–100 × 34–50 mcm

Abomasum

Egg

High

Teladorsagia (formerly Ostertagia) circumcincta and Ostertagia trifurcata (medium or brown stomach worms)

Adults: 6–10 mm

Eggs: 65–100 × 34–50 mcm

Abomasum

Egg

High

Mecistocirrus digitatus

Adults: 40 mm

Eggs: 65–100 × 34–50 mcm

Abomasum

Egg

Low

Trichostrongylus spp (stomach or bankrupt worms)

Adults: 4–7 mm

Eggs: 65–100 × 34–50 mcm

Abomasum, small intestine

Egg

Medium-high

Nematodirus spp (thread-necked intestinal worms)

Adults: 10–23 mm

Eggs: 175–260 × 106–110 mcm

Small intestine

Egg

Medium

Strongyloides papillosus (intestinal threadworm)

Adults: 3.5–10 mm

Eggs: 40–60 × 32–40 mcm

Small intestine

Larvated egg

Low

Aonchotheca (formerly Capillaria) longipes

Adults: 8–20 mm

Eggs: 45–50 × 22–25 mcm

Small intestine

Egg with bipolar plugs

None

Bunostomum spp and Gaigeria spp (hookworms)

Adults: 12–26 mm

Eggs: 79–97 × 47–50 mcm

Small intestine

Egg

Low-medium

Moniezia spp (tapeworms)

Adults: Width 15–25 mm, length variable

Eggs: 65–75 mcm in diameter

Small intestine

Egg or segments

Low

Thysanosoma actinioides (fringed tapeworm)

Adults: 25–50 mm

Eggs: 30 × 20 mcm

Small intestine

Egg or segments

Low

Oesphagostomum columbianum (nodular worm)

Adults: 12–21 mm

Eggs: 73–89 × 34–45 mcm

Cecum, colon

Egg

Low-medium

Chabertia ovina (large-mouth bowel worm)

Adults: 12 mm

Eggs: 65–100 × 34–50 mcm

Colon

Egg

Low-medium

Trichuris spp (whipworms)

Adults: 35–80 mm

Eggs: 70–80 × 30–42 mcm

Cecum, colon

Egg with bipolar plugs

Medium

Skrjabinema spp (pinworms)

Adults: 110–500 × 3–10 mcm

Eggs: 47–63 × 27–36 mcm

Colon, rectum

Egg on perianal skin

None